Electrical submersible pumps (ESP) are widely used to pump oil production wells. A typical ESP has a rotary pump driven by an electrical motor. A seal section is located between the pump and the motor to reduce the differential between the well fluid pressure on the exterior of the motor and the lubricant pressure within the motor. A drive shaft, normally in several sections, extends from the motor through the seal section and into the pump for rotating the pump. The pump may be a centrifugal pump having a large number of stages, each stage having an impeller and diffuser.
During operation, the impellers create thrust, which can be both in downward and upward directions. The impellers transmit the thrust in various manners to the diffusers. Some pumps are particularly used in abrasive fluid environments. In those pumps, a thrust runner is coupled to the shaft to receive thrust from one or more impellers. A bushing secured into a receptacle in the diffuser receives the thrust and transfers the thrust to the diffuser. The thrust runner and the bushing may be formed of an abrasion resistant material, such as tungsten carbide, that is harder than the material of the diffuser. The bushing is commonly installed in the receptacle with a press fit.
Damage and misalignment may occur When the hard bashing is press fit into the diffuser. The wear resistant bushing may misalign slightly when pressed into the diffuser receptacle. During operation, load concentrations may occur, causing the carbide material to crack or chip. Some pumps tend to vibrate, particularly at higher fluid flow pressures, and the vibration can lead to carbide chattering. The bearing surfaces are subject to intermittent loading due to gas slugging fluid production, creating shock. Heat is generated by the bearing surfaces, which can cause damage to the bearings.